1. Field of the Invention
The invention relates to optical devices, and in particular to optical devices with reduced electrical consumption and enhanced shockproof capability.
2. Description of the Related Art
Automatic displacement drive devices applied in lens modules may employ drivers providing rotational power with a rotational axis thereof paralleling an optical axis of the lens module, or drivers providing movement power with the moving direction thereof paralleling the optical axis of the lens module.
An example of a driver providing rotational power with a rotational axis thereof paralleling an optical axis of the lens module is a stepping motor. Such drivers require additional transmission-conversion mechanisms to enable the lens module to move along an axis parallel to the optical axis. When the lens module arrives at a final position, no electricity is required to maintain the lens module therein. However, such drivers have many components. Thus, the structure of such drivers is complicated, and the size thereof cannot easily be reduced.
An example of a driver providing movement power with the moving direction thereof paralleling the optical axis of the lens module is a voice coil motor. Such drivers directly adjust the position of the lens module. Compared with rotational power drivers, such drivers have fewer components and are smaller. However, when the lens module arrives at a final position, electricity must be continuously supplied thereto and simultaneous control maintained in order to keep the lens module at the final position. Accordingly, automatic displacement drive devices employing such drivers consume a great deal of electrical power. The portability of cameras or optical devices employing such drivers is thus adversely affected. Additionally, such drivers provide poor shockproof capability.
Referring to FIG. 1, U.S. Pat. No. 6,856,469 discloses a conventional lens drive device with a magnetic member 9, a spacer member 12, and a spring member 50 arranged parallel to an optical axis of a lens 2. The lens 2 is retained at retaining positions by magnetic attraction between a drive magnet 6 and the magnetic member 9 and by the spring member 50. However, electrical power is required to retain the lens 2 at the retaining positions, and the relationship between the moving position of the drive magnet 6 and magnetic member 9 and the variation of magnetic force thereof is nonlinear. Accordingly, positioning control of the lens 2 in the conventional lens drive device is difficult.
Moreover, as shown in FIG. 2A and FIG. 2B, WO2005/060242 discloses a conventional brake device capable of releasing or holding a lens module 608 at specific positions. The brake device comprises a brake and holding member 621, a magnetic member 627, a coil 623, a rotating shaft 622, and a resilient element E. When the coil 623 is energized by application of an electric current, magnetic attraction is generated between the magnetic member 627 and the coil 623. At this point, the brake and holding member 621 rotates around the rotating shaft 622, releasing the lens module 608, as shown in FIG. 2B. When the coil 623 is not energized by application of the electric current, no magnetic attraction is generated between the magnetic member 627 and the coil 623. At this point, the brake and holding member 621 rotates to an initial position around the rotating shaft 622 by resilience provided by the resilient element E, holding the lens module 608, as shown in FIG. 2A. However, the conventional brake device has many components and complex structure and is not easily assembled and miniaturized.
Additionally, as shown in FIG; 3A and FIG. 3B, Japan Patent Publication No. 2005-128405 discloses a conventional lens drive device 1. An upper spring 9 and a lower spring 11 enable precise movement of a lens module (including a lens 20, an upper cover 24, a lower washer 17, a coil 15, and a lens supporting base 7) and reduce friction during movement thereof. The upper spring 9 and lower spring 11 may be regarded as extensions of the coil 15, serving as conductors at ends thereof. Grooves 37 on an upper frame 23 and ribs 31 on the lens supporting base 7 bear impact or vibration generated by contact between a moving assembly (including the lens 20, upper cover 24, lower washer 17, coil 15, and lens supporting base 7) and a stator (including the upper frame 23, a yoke 3, and a magnet 13), controlling a deviation value of the moving assembly with respect to an optical axis within an acceptable scope and preventing excessive rotation of the lens 20 from adversely affecting other mechanisms in the lens drive device 1. Nevertheless, electrical power is also required to maintain the moving assembly of the lens drive device 1 in specific positions, thus reducing long-term positioning capability thereof.
Hence, there is a need for optical devices, for fixing and releasing a lens module, with reduced size and power consumption, simplified structure, and enhanced shockproof capability.